Chemical mechanical polishing (CMP) is one process commonly used in the manufacture of high-density integrated circuits to planarize or polish a layer of material deposited on a substrate. A carrier head may provide the substrate retained therein to a polishing station of a polishing system and controllably urge the substrate against a moving polishing pad. CMP is effectively employed by providing contact between a feature side of the substrate and moving the substrate relative to the polishing pad while in the presence of a polishing fluid. Material is removed from the feature side of the substrate that is in contact with the polishing surface through a combination of chemical and mechanical activity. Particles removed from a substrate while polishing become suspended in the polishing fluid. The suspended particles are removed while polishing the substrate by the polishing fluid.
As the feature size of the device patterns get smaller, the critical dimension (CD) requirement of features becomes a more important criterion for stable and repeatable device performance. When the CD of features shrink to sizes less than 20 nm, submicron scratches become more and more critical for device yield improvement. The CMP has a carrier head which typically includes a retaining ring that circumscribes the substrate and facilitates holding the substrate in the carrier head. During polishing, the substrate may come into contact with the retaining ring and break free portions of the retaining ring as well as adhered materials and introduce loose materials into the polishing process. These loose materials may come into contact with the substrate and polishing surface during polishing and contribute to microscratches (<100 nm) on the substrate as well as other types of defects such as line distortion and check mark defect.
Therefore, there is a need for an improved retaining ring.